1. Field Of Invention
This invention relates to apparatus and methods to accurately scan and record skin surface topography. More particularly, the present invention has embodiments which can accurately scan fingerprints.
2. Description Of Prior Art
It has been established that fingerprints as well as other epidermal topography can be used to uniquely identify individuals. Such identification has been used for many years to help solve crimes, provide positive identification for security, identify missing persons, etc.
More recently devices have been introduced to electronically scan fingerprints and other skin surfaces. These devices typically produce signals which are inputted into computers which in turn match the signals to images stored in computer memory.
These scanning devices can generally be divided into two groups: those using optics to scan, and those using mechanical sensing means.
Most of the devices using optics have the finger tip, or other skin surface to be scanned, placed on a transparent surface. Light is shown from the underside of the transparent surface toward the finger tip or skin surface, and the reflection of the light is detected by optical sensors which output a signal containing the fingerprint or other skin surface image.
Devices using mechanical sensing means to survey finger tip, or other skin surface, have the finger tip or skin surface to be scanned placed on a sensor plate which detects minute differences in pressure caused by skin surface features.
Both of these approaches to scanning fingerprints and other skin surfaces have substantial disadvantages.
Devices using optics rely on clear and distinct images of skin surface features being displayed on the transparent surfaces on which the skin surfaces are placed. All finger tips, even freshly washed finger tips, leave residues of oil and moisture on surfaces they contact. Such residues are what allow criminologists to obtain latent fingerprints hours, days and even weeks after a criminal has touched a surface.
A fingerprint, or other skin surface, scanning device which relies on optical reflection from a transparent surface can be confused by such residues and thus such devices tend to report erroneous skin surface features after several uses. Excessively oily, dirty or moist skin also tends to make devices relying on transparent surface optics less accurate.
Devices relying on mechanical sensing means to scan finger tip or other skin surface features generally utilize matrices of delicate pressure sensing circuits. Such matrices tend to be temperamental under ideal conditions. Temperature changes, residues, moisture, and sun light exacerbate problems of accurate reporting by these devices.